The Pakistani prosecutor investigating the assassination of the country's former Prime Minister, Benazir Bhutto, has been shot and killed. Chaudry Zulfikar Ali had also been involved in the investigation into the Mumbai massacre in 2008. His killing comes at a tense time as Pakistan prepares for national elections next week. An anti-Taliban candidate in Karachi was also murdered today. Sarah Smith has this report.

By Wajahat S. Khan and Ian Johnston, NBC News

ISLAMABAD, Pakistan -- A prosecutor investigating the assassination of former Pakistani Prime Minister Benazir Bhutto was shot dead in a “targeted killing” in Islamabad on Friday, police sources said.

Several attackers on motorcycles and in a taxi opened fire on Chaudhry Zulfikar’s car as he drove to work at about 7 a.m. local time (10 p.m. ET on Thursday), the sources said.

His guard, a paramilitary soldier provided by the government, and a woman on the side of the road were both shot and wounded in the attack. The woman was also hit by Zulfikar’s white Toyota when it veered off the road.

Security expert Amir Rana told Reuters that Zulfikar was probably a marked man because he had been prosecuting militants who were jailed in connection with Bhutto's death or other cases.

Bhutto was killed in a gun and suicide bomb attack carried out by a 15-year-old boy after an election rally in the city of Rawalpindi, just weeks after she returned to Pakistan from years in self-imposed exile in a bid to reclaim office.

Bhutto was a fierce critic of Pakistan's Taliban and Islamist groups that had been supported by some elements of Pakistan's military.

Her death was one of the most shocking events in the country's turbulent history, and had a similar impact on the nation as the 1963 assassination of President John F. Kennedy in the United States.

Speculation has lingered that Bhutto was the victim of a plot by allies of General Pervez Musharraf, the president at the time, who did not want her to come to power.

The killing of the prosecutor comes days after a Pakistani court put Musharraf on a 14-day judicial remand for charges of failing to provide adequate security for Bhutto before her assassination.

The former army chief, who has always denied responsibility for Bhutto's death, returned to Pakistan in March after nearly four years of self-imposed exile to contest the May 11 general election. But he has since been banned from politics for life.

In 2010, a United Nations Commission of Inquiry report concluded security arrangements for Bhutto were “fatally insufficient and ineffective” and that the investigation of her death had been “prejudiced,” describing it as a whitewash.

In a statement issued about the report, the U.N. said the government “was quick to blame local Taliban commander Baitullah Mehsud and al Qaeda although Ms. Bhutto’s foes potentially included elements from the establishment itself.”

“A range of government officials failed profoundly in their efforts first to protect Ms. Bhutto and second to investigate with vigor all those responsible for her murder, not only in the execution of the attack, but also in its conception, planning and financing,” the commission said.

“Responsibility for Ms. Bhutto’s security on the day of her assassination rested with the federal government, the government of Punjab and the Rawalpindi District Police,” it added. “None of these entities took necessary measures to respond to the extraordinary, fresh and urgent security risks that they knew she faced.”